Re: Re: xm list dropping domain?

[Mike Wray <mike.wray@hpl.hp.com>]

Tim Freeman wrote:
> Thanks for the information Mike,
> 
> I supposed it was getting destroyed, hmm.  I'm making the controller
> part of a grid service and the VM's are distinguished by an assigned
> distinguished name which maps to a local name (so that ID #s can
> change).  The controller is only dealing in local names now.  It looks
> like one of the domain events is restart:
> 

The domain exits with code reboot:
> (event xend.domain.exit (gridvm1 3 reboot))

This is the restart being scheduled:
> (event xend.domain.restart (gridvm1 3 schedule))

Now the domain gets destroyed and goes away:
> (event xend.domain.destroy (gridvm1 3))
> (event xend.domain.died (gridvm1 3))

Now the domain has gone we can restart it:
> (event xend.domain.restart (gridvm1 3 begin))

Between the died event and the create event gridvm1 will
not appear in 'xm list'.
> (event xend.domain.create (gridvm1 3))

The create succeeded so we get a restart success:
> (event xend.domain.restart (gridvm1 3 success))

The domain starts to run:
> (event xend.domain.unpause (gridvm1 3))
> 
> ..where "gridvm1" is the local name.  So I don't think a domain object
> is necessary, couldn't I poll 8001 for any changes concerning the local
> name (as long as nothing at a higher level started a domain with the
> same name in that window)?.  That's pretty cool, I didn't know you could
> receive the events, I thought you could only 'ask.'
> 
> That makes me think I should write a polling thread that any class could
> register callbacks with?  My thinking is that the 'right way' is to
> decouple any higher level functionality.  Unless I'm missing a
> programming trick here..

What I do in java is use a thread to read the events out of of the socket
and post them to a class handling the usual 'listener' pattern
so that things can register callbacks. Pretty much as you suggest.
In python you could use asyncore or twisted to avoid threads/blocking.

Hope this helps,

Mike

> 
> On Tue, 5 Oct 2004 14:25:58 +0100 
> Tom Wilkie <tw275@cam.ac.uk> wrote:
> 
> 
>>>From python you can use XendClient to call the api directly - either
>>>synchronously or asynchronously. From Java you can use Jakarta commons
>>>httpclient, and from C you can use libcurl (see the xfrd source in 
>>>xen).
>>>
>>
>>I wrote a simple interface to xend in java for the high-xeno stuff.  
>>Let me know if you need it, I don't think that repository is public.
> 
> 
> Thanks, I would definitely like to take a look.  I started an http
> interface, but I do need to think about all of this some more (if I
> combined or made improvements I'd make that available to anyone also).
> 
> Thanks to you both for you help!
> 
> Tim
> 
> 
> 
> 
>>Cheers
>>
>>Tom
>>
>>
>>
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> 
> 
> 



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